Reamplifying- system



Jan. 16, 1928;

H. w. NICHOLS.

REAMPLIFYING SYSTEM;

FILED JULY 7, 1921.

Patented Jan. 16, 1923. I

UNITED stares PATENT OFFICE.

HAROLD W. NICHOLS, OF MAPLEWOOD, JERSEY, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

nEaMPLirYINe SYSTEM.

Application filed July 7,

To all whom may concern Be it known that I, HAROLD W. Nrcrioiis, a citizen of the United States, residing at loial'JlBWOOLl, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Reamplifying Systems, of which the followin is a full, clear, concise, and exact description.

This invention relates to reamplifying systems.

One object of the invention is to provide an arrangement which will selectively aniplify electrical waves of a given frequency, or range of frequencies, without amplifying disturbing energy or other waves of considerably different frequency.

A feature of the invention is a reamplifying arrangement which is substantially independent in its frequency selection of one kind of reactance.

Another feature of the invention is a thermionic oscillator in which the frequency of the oscillations produced is determined by constants of the thermionic device and an associated network and is substantially independent of one kind of reactance.

An additional feature of the invention consists in using one element of the feedback circuit of an amplifier to serve also as a radio receiving antenna.

A. further feature of the invention is a radio receiving system, the selectivity of which is substantially independent of one kind of reactance and hence avoids, to a large degree, the tendency of the ordinary tuned circuit to set up natural oscillations when disturbed by interfering energy.

A still further feature of the invention is a filter through which energy is transmitted and thereafter reimpressed upon the same filter in phase with the energy originally applied.

According to the present invention, a three-element electric discharge device or other equivalent amplifier is provided withv a feedback circuit connecting its output circuit to its input circuit. This feed-back circuit consists of a network having effective reactance of substantially one kind only, and the amplifier may be operated to produce continuous oscillations of a frequency determined by its own character- 1921. Serial No. 482,912.

istics and those of the network, or it may be operated at such a degree of amplification as to rearnplify impressed waves witlr out maintaining continuous oscillations. A reactance element of the feed-back network may serve also as an antenna and the amplifying circuit may in that case, serve for the reception of radio signal waves.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method. of operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figs. 1 to 4 inclusive illustrate different arrangements of reamplifying circuits; Fig. 5, an application of the circuit of Fig. l to production and transmission of alternating current; Fig. 6, a radio receiving system including a reamplifying arrangement substantially free from reactance of one kind and Figs. 7 and 8, modified forms of radio receiving systems.

Referring to Fig. 1, a thermionic threeelement amplifier 1, preferably highly evacuated, is shown associated with a network consisting of a plurality of meshes or sections, each having a series resistance R and a shunt capacity element C, and substantially free from inductance. The amplifier is provided with an impedance control element or grid 2, a hot filament cathode 3, and an anode or plate electrode 4:. The space current for the amplifier is supplied by a source E, in series with a very large resistance R. In the circuit; of this figure and in those of each of the following figures a source E may be used to maintain the grid at the most desirable potential with respect to the cathode.

The input terminals of the amplifier, namely, those leading to the cathode and grid are connected to points a, b, the terminals of the end capacity element C of the network. The output terminals of the amplifier, namely, those leading to the cathode and plate, are connected to points 0, d, the terminals of the end capacity element C at the opposite end of the network from terminal points a, and 5. A varying E. M. F.

applied to terminals or and Z) will accordingly be impressed upon the input circuit of the amplifier to produce an amplified E. M. F. across the output terminals 0 and (Z. The network in transferring amplified energy from points 0 and d to points a and b, operates both to shift its phase and to attenuate it. Each section of the network shifts the phase of the transmitted wave by a certain amount. If the phase shift throughout the entire net work, that is, from points 0 and (Z to points a and b, is substantially 180 degrees or 180 degrees plus560 degrees or a multiple of 360 degrees, the amplified energy transmitted from terminals 0, (.Z to terminals bwill be in phase agreement with the applied E. M. F., thus giving rise to re-amplification. If the total attenuation which the network causes, is less than the amplification which occurs in consequence of the operation of amplifier 1, the amplified energy which reaches terminals 0:, b, will, after attenuation in the network, be greater than the energy initially impressed at these terminals, and if the amplified energy is in phase agreement with the impressed energy, the an'qlifier and network may act as an oscillator.

The sections of the network may be made alike, in which case the network is termed iterative, or they may be unlike. In the case of the iterative network, the phase shift and attenuation are the same for each mesh audit is accordingly possible to readily calculate the phase shift and attenuation produced by the network as a Whole or conversely to determine the constants of the network which will produce a definite phase shift and attenuation at a given frequency. The method of calculation for iterative networks is similar to that by which the constants are determined for reactive iterative networks as set forth in United States pat ents to G. A. Campbell, Nos. 1,227,113 and 1,227,114 patented li Iay 22, 1917. The frequency of the oscillations and the amplifying power necessary to produce them may be calculated in the manner outlined in the article entitled The audionas circuit element Physical Review, N. S. volume 13, No. 6, June, 1919. Note particularly pages 412 to 4142 inclusive. 1 i

Fig. 2 discloses an arrangement similar to that of Fig. 1, but including a network having shunt resistances It and series capacity elements C and substantially, free from, inductance. In this arrangement no separate space current path is necessary for the source E Fig. 3 illustrates an amplifying arrangement having a network with series resistances R and shunt inductance elements I1 and substantially freefrom capacity reactance. converse arrangement of Fig. 3 with series inductances L and shunt resistances R- Fig. 4 illustrates thecillators of each of the four types described with but two meshes in the feed-backnetwork. In general, it will'be found desirable to use a. greater number of meshes. For the arrangement of Figs. 1 and 3, the frequency of the oscillations produced or for which the device will act as a reamplifying arrangement, if not adjusted to the 0s. cillating condition, decreases with an in creasing number of sections in the network. The higher frequency oscillations will therefore be obtain d with but two sections, and the lower frequencies withlarger num= bers of sections. The frequency of the oscillations produced is a function of both the characteristics of the network and of the voltage amplifying factor of the amplifier. For the circuit arrangements of Figs. 1 and 8, increasing the amplifying factor, increases the frequency and decreasing the amplifying factor, decreases the frequency, the circuit being otherwise unvaried. The arrangements of Figs 2 and 4E produce their lowest frequency oscillations with two meshes in the feed-back networl. As the number of meshes is increasechthe frequency of the oscillations produced by these arrangements increases. With a given network, the oscillators of these two figures produce increasing frequency oscillations as the yoltage amplifying power of their amplifiers is decreased and vice versa.

Fig. 5 illustrates an oscillator of the type of 1 in which the feed-back circuit comprises two meshes. A thermionic amplifier A of the Well-known highly evacuated three-element electric discharge type has its input circuit connected directly across the terminals of a series resistance 5 in the feedback network and serves to supply amplified oscillations to a work circuit 6 coupled to the output circuit of the a1n plifier by a transformer 7. Space current is supplied to the discharge device of the oscillator by source E through a path including extremely high impedance elements L and R This path'thereforeplays 110' essential part in the determination of the oscillation frequencies. The grid of the oscillator is polarized by a source E in series with a very large inductance L In a given example, the internal space currentohms and each of the series resistances R The voltage of Cir of the network were oi 70,000 chins magnitude. The calculated frequency oi? the 0s cillator from the formula which may be readily deduced for this par-- ti cular network by the methods ofthe Physical Review article, previously cited, is about 1,100 cycles. In this "formula, represents the frequency oi the oscillations in cycles per second; C, the capacityoi each shunt condenser oi the network; R the internal space current resistance of the oscillator tube, and ll, the series resistance of each oi? the elements oi the network. The ij'requency .of the oscillations produced by this arranger zli) ment was measured and found to agree very closely with that calculated.

F i 6 illustrates a. reaniolif in circuit adapted to serve as aradio receiver. A. thermionic amplifier 10 is provided with a cathode 11, anode 12 and impedance control element 13.. Its input circuit includes an inductance L coupled to an inductance L, in the plate circuit, a resistance R in shunt to L and an inductance L which serves as a loop receiving antenna. The plate circuit includes, in addition to inductance L and the space current source E a receiver or other signal translating element 1. The circuit is arranged to be substantially free of capacity reactance, and the arrangement operates to. reamplil'y waves or produce oscillations, the frequency of which is determined by the resistance and inductance of the network and the internal space current resistance of the tube. Any casual capacities of this arrangement are of such an order that they have negligible effect in determining the frequency of the oscillations dall No. 1330-l7l, patented Feb. 10, 1920."

Finally, the oscillator may, if desired, be arranged to oscillate at a frequency different from that 01" received oscillations so that the receiving system may operate according to the well known heterodyne method. Whichever of these three operations occurs, the received oscillations will bedemodulated to yield intelligible signals in the receiver 1.

Figs. 7 and 8 disclose reamplifying arrangements arranged to function in the same general manner as that of Fig. 6. The circuit of Fig. 7 is analogous tothat of Fig. 1, but has fewer meshes and has its end capacity element formed by a capacity antenna 14:. This arrangement reamplifies or oscillates at a frequency substantially in- 1 i a cation in other relations and are theretore not to be limited to an of the particular arrangements or uses suggested in the foregoing disclosure, but only y the scope of the appended claims.

What is claimed is:

l. A network comprising a plurality of meshes, means for impressing oscillations upon one portion oil? said network. means for feeding back a part of the energy oi the'impressed oscillations transmitted through said network to impress this energy upon the same portion oil the network in phase with the oscillations originally impressed thereon.

2. A network comprising a plurality of meshes and including an antenna, 'n'ieans for impressing oscillations upon one portion of said network, means for feeding back a part of the energy of the oscillations transmitted through said network and for reimpressing the energy fed back upon the same portion of the network in phase with the oscillations originally impressed thereon.

3. An amplifier having an input circuit and an outputcircuit, and a network connected to each of said circuits to feed back amplified energy lfrom said output circuit to said input circuit, said network serving to determine the phase of the energy fed back and being substantially free from one kind of react-ance.

4:. An amplifier having input and output circuits and means substantially free from reactance of one kind for feeding back amplified energy from said output circuit to said input circuit, said means comprising an iterative network of similar sections.

5. An oscillator comprising an amplifier having an input circuit, an output circuit, and means for feeding back amplified energy from said output circuit to said input circuit, said means consisting of an iterative net work including' reactance of one kind only.

6. An amplifier having input and output circuits and connecting means to feed back amplified energy from said output circuit to said input circuit comprising a network having substantially only one kind of reactance, one of the reactance elements: of said network consisting of a receiving element for radiant energy.

7. An amplifier having an input circuitand an output circuit, a network connected to each of said circuits to feed back amplified energy from said output circuit to said input ing substantially only one kind of reactance,

one of the reactance elements of said net Work consisting of a wave energy receiving element.

9. An amplifier having aninput circuit, an output clrcuit, and means for feeding back amplified energy from. said output circuit to said input circuit, said means consisting of an iterative network, each section of which comprises a resistance element and a reactive element consisting of reactance of one kind only, one of the elements of said net- Work consisting of a receiving element for external energy.

10. An amplifier having input and output circuits, and connectingmeans to feed back amplified energy from said output circuit to said input circuit comprising an iterative network having substantially capacitative reactance only.

11. An amplifier having input and out put circuits, and connecting means to feed back amplified energy from said output circuit to said input circuit comprising a network havlng substantlally capacltative reactance only, one of said capacltatlve reactance elements consisting of a wave energy receiving element.

In Witness whereof, I hereunto subscribe" my name this 1st day of July A; D., 1921.

' HAROLD W. NICHOLS. 

